This invention relates to energy conservation systems and more particularly to energy conservation systems for use with a power source which supplies power over premises wiring to utilization equipment such as lighting equipment and the like.
The cost of energy has made it increasingly desirable to conserve it by reducing wasteful and unnecessary power consumption by equipment, such as unutilized lights, fans and the like, within a building. Lights are often left burning after hours in many areas where they are not needed. The yearly cost of this in a large building can be thousands of dollars.
Automated lighting control systems have been proposed to solve this problem, but most require either extensive rewiring in the building or do not permit local override of the automatic control. Extensive rewiring is often required because at the most accessible points, the light switches, usually only one side of the line is available. One approach to automated control of lighting, or other utilization equipment, which does not require extensive rewiring involves impressing a control signal or signals on the a.c. power lines. However, this approach requires a detector circuit at each point in the circuit at which automated control is desired. In addition any transformers in the circuit distort the impressed control signal or signals. Systems using this latter approach are shown in U.S. Pat. Nos. 3,359,551 and 4,217,646.